Abstract

Audiometric thresholds and otoacoustic emissions(OAEs) were measured in 285 U.S. Marine Corps recruits before and three weeks after exposure to impulse-noise sources from weapons’ fire and simulated artillery, and in 32 non-noise-exposed controls. At pre-test, audiometric thresholds for all ears were HL from and HL at . Ears with low-level or absent OAEs at pre-test were more likely to be classified with significant threshold shifts (STSs) at post-test. A subgroup of 60 noise-exposed volunteers with complete data sets for both ears showed significant decreases in OAE amplitude but no change in audiometric thresholds. STSs and significant emission shifts (SESs) between 2 and in individual ears were identified using criteria based on the standard error of measurement from the control group. There was essentially no association between the occurrence of STS and SES. There were more SESs than STSs, and the group of SES ears had more STS ears than the group of no-SES ears. The increased sensitivity of OAEs in comparison to audiometric thresholds was shown in all analyses, and low-level OAEs indicate an increased risk of future hearing loss by as much as ninefold.

Received 13 June 2008Revised 20 November 2008Accepted 21 November 2008

Acknowledgments:

Thanks to Linda Westhusin, Michael McFadden, Denise Cline, Jackie Adler, Joy Houston, and Brian Ferris for their assistance with data collection. A special thanks to the staff and recruits of the Marine Corps Recruit Depot (MCRD) San Diego and Charles Jackson of the Naval Medical Center San Diego Occupational Audiology Department. Thanks to Tom Taggart for his input into the overall experimental design, help with logistics, and feedback on preliminary analyses. Thanks to Chris Shera for helpful discussions on the theoretical aspects. Thanks to the two anonymous reviewers whose considered opinions substantively improved the manuscript. This research was supported primarily by grants from the Office of Naval Research. The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, the Department of Defense, or the United States Government.